| Strawberry(Fragaria x ananassa Duch.)is a perennial herb of the genus Strawberry in the family Rosaceae,which is highly effective and planted everywhere and plays an important role in rural revitalization.Strawberries are divided into seasonal strawberries and perpetual strawberries.Seasonal strawberries bear fruits in winter and spring,while perpetual strawberries are harvested in summer and autumn,which can realize annual supply of strawberries.The Yangtze Delta region is a major province for winter and spring strawberry production,but few perpetual strawberries are grown due to high summer temperatures,and the reason for this is the lack of varieties suitable for summer and autumn cultivation.In this study,36 perpetual strawberry varieties(strains)were studied for their agronomic traits,photosynthetic characteristics and red leaf disease resistance in summer and autumn.the agronomic traits and net photosynthetic correlations were analyzed,the coefficient of variation of traits and genetic diversity index between varieties(strains)were analyzed,the potential of hybrid combinations of different parents was evaluated,strawberry germplasm suitable for planting in Nanjing and other high summer temperature areas was screened.It provides data support and theoretical basis for the production of strawberries in all seasons in the Yangtze Delta region and the excellent germplasm breeding of strawberries in China.The main results were as follows:1.36 strawberry germplasm were rich in genetic variation for all traits.11 agronomic traits had diversity indices ranging from(Number of stolons)1.38 to2.09(Root diameter)and coefficients of variation ranging from 7.60 %(Chlorophyll content)to 163.91 %(Number of stolons);4 photosynthetic parameters had diversity indices ranging from(Stomatal conductivity)1.98 to2.06(Net photosynthetic rate)and the coefficients of variation ranging from(Net photosynthetic rate)1.84% to 4%(Stomatal conductivity),8 fruit quality diversity indices ranged from(Longitudinal diameter)1.81 to 2.04(Soluble sugar);and the coefficients of variation of fruit quality index was between(Soluble solids)1.55% and 7.07%(Hardness).The correlation analysis of agronomic traits showed that the number of inflorescences was highly significantly and positively correlated with leaf number,single fruit weight,hardness,soluble solids,fruit longitudinal diameter and fruit transverse diameter,while the number of inflorescences was significantly and positively correlated with net photosynthetic rate;single fruit weight was highly significantly and positively correlated with the number of inflorescences,hardness,soluble solids,fruit longitudinal diameter,and fruit transverse diameter.Based on the analysis of agronomic traits and photosynthetic characteristics of nested hybrid populations,the results showed that Ning Yu x 47,Meng te rui x 47,Bo te la x47,Ning Yu x SJ-SS-1G1,Ning Yu x Tian xin,and Hong jia x Big chun xiang were superior;based on the principal component analysis and affiliation function analysis.The results showed that the cumulative contribution of the first four principal components was 84.777%,and the affiliation function scores of each germplasm ranged from 0.1 to 0.93.Among them,the comprehensive ranking score of the four germplasm types DN51 C was greater than 0.9,indicating excellent comprehensive performance.2.The study of red leaf disease resistance showed that red leaf disease occurred in all germplasm,and 12 germplasm were highly resistant,5germplasm were resistant,3 germplasm were moderately resistant,6 germplasm were susceptible,and 10 germplasm were highly susceptible;’Hong jia’,’11-650’,’21-4G’,’L121’,’2-604’ and ’DN51C’ were strong disease-resistant germplasm.Based on the analysis of resistance to red leaf disease in nested hybrid populations,the results showed that four populations had better resistance to red leaf disease,including Hong jia x 47,Bo te la x47,Ning yu x Tian xin,and Hong jia x Da chun xiang.In this study,superior strains and germplasm screening was conducted in Nanjing,a representative area of the Yangtze Delta region with high temperature.Ultimately,five superior strawberry germplasms with excellent performance and strong resistance to red leaf disease and four superior strains were selected,including DN51 C,21-4G,L121,11-650,2-604 and Ning Yu x Tian xin,Ning Yu x SJ-SS-1G1,Ning Yu x 47,Hong jia x Da chun xiang.This study provides a reliable theoretical basis and data support for summer strawberry planting and parental selection of new varieties in the Yangtze Delta region. |
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